TauP Pierce

TauP Pierce uses a model like TauP Time but determines the angular distances from the epicenter at which the specified rays pierce discontinuities or specified depths in the model.

The usage is:

Usage: taup pierce [arguments]
  or, for purists, java edu.sc.seis.TauP.TauP_Pierce [arguments]

Arguments are:
-ph phase list     -- comma separated phase list
-pf phasefile      -- file containing phases

-mod[el] modelname -- use velocity model "modelname" for calculations
                      Default is iasp91.

-h depth           -- source depth in km

--stadepth depth   -- receiver depth in km
--scat[ter] depth deg   -- scattering depth and distance

Distance is given by:

-deg degrees       -- distance in degrees,
-km kilometers     -- distance in kilometers,
                      assumes radius of earth is 6371km,

or by giving the station and event latitude and lonitude,
                      assumes a spherical earth,

-sta[tion] lat lon -- sets the station latitude and longitude
-evt       lat lon -- sets the event latitude and longitude

or by giving the takeoff angle,
--takeoff angle    -- takeoff angle from the source
                      zero is down, 90 horizontal, 180 is up

or by giving the ray parameter,
--shootray param   -- ray parameter from the source in s/deg
                      up or down is determined by the phase


-az azimuth        -- sets the azimuth (event to station)
                      used to output lat and lon of pierce points
                      if the event lat lon and distance are also
                      given. Calculated if station and event
                      lat and lon are given.
-baz backazimuth   -- sets the back azimuth (station to event)
                      used to output lat and lon of pierce points
                      if the station lat lon and distance are also
                      given. Calculated if station and event
                      lat and lon are given.

--first            -- only output the first arrival for each phase, no triplications
-rev               -- only prints underside and bottom turn points, e.g. ^ and v
-turn              -- only prints bottom turning points, e.g. v
-under             -- only prints underside reflection points, e.g. ^

-pierce depth      -- adds depth for calculating pierce points
-nodiscon          -- only prints pierce points for the depths added with -pierce


-o [stdout|outfile]         -- output is redirected to stdout or to the "outfile" file
--prop [propfile]   -- set configuration properties
--debug             -- enable debugging output
--verbose           -- enable verbose output
--version           -- print the version
--help              -- print this out, but you already know that!

The --rev, --turn and --under flags are useful for limiting the output to just those points you care about. The --pierce depth option allows you to specify a ``pierce’’ depth that does not correspond to an actual discontinuity. For instance, where does a ray pierce 300 kilometers above the CMB?

For example:

taup pierce --mod prem -h 200 -p S,P --deg 57.4

would give you pierce points for S, and P for a 200 kilometer deep source at a distance of 57.4 degrees.

While

taup pierce --turn --mod prem -h 200 -p S,P --deg 57.4

would give you just the points that each ray turns from downgoing to upgoing.

Using -rev would give you all points that the ray changes direction and -under gives just the underside reflections.

Using the -pierce option

taup pierce --mod prem -h 200 -p S --sta 12 34.2 --evt -28 122 --pierce 2591 --nodiscon

would give you just the points at which S crossed a depth of 2591 kilometers from an event at ($28^circ$ S, $122^circ$ E) to a station at ($12^circ$ N, $34.2^circ$ E). Because we specified the latitudes and longitudes, we also get the latitudes and longitudes of the pierce points, useful for making a map view of where the rays encounter the chosen depth. Here is the output, distance, depth, latitude and longitude, respectively.

> S at  1424.11 seconds at    93.70 degrees for a    200.0 km deep source in the prem model with rayParam    8.717 s/deg.
   31.56  2591.0  552.57    -17.87     89.41
   61.47  2591.0  822.01     -3.89     62.40